Wireless transmission systems may use transmit diversity, whereby signals are transmitted to a receiver using a plurality of transmit antennas. Typically, such transmit diversity systems are intended to increase network capacity and reduce the signal degradation caused by multi-path and fading. A phase difference between signals transmitted by two or more antennae may be calculated according to a modulation or perturbation algorithm, and implemented using a programmable phase shifter. There is a need for an improved implementation of controlling the phase difference between two or more transmit diversity signal paths.